This invention relates to self-contained airbag systems and more particularly to self-contained side impact airbag systems.
Self-contained airbag systems contain all of the parts of the airbag system within a single package, in the case of mechanical implementations, and in the case of electrical or electronic systems, all parts except the primary source of electrical power and, in some cases, the diagnostic system. This includes the sensor, inflator and airbag. Potentially these systems have significant cost and reliability advantages over conventional systems where the sensor(s), diagnostic and backup power supply are mounted separate from the airbag module. In mechanical implementations in particular, all of the wiring, the diagnostic system and backup power supply are eliminated. In spite of these advantages, self-contained airbag systems have only achieved limited acceptance for frontal impacts and have so far not been considered for side impacts.
The xe2x80x9call-mechanicalxe2x80x9d self-contained systems were the first to appear on the market for frontal impacts but have not been widely adopted partially due to their sensitivity to accelerations in the vertical and lateral directions. These cross-axis accelerations have been shown to seriously degrade the performance of the most common all mechanical design that is disclosed in Thuen, U.S. Pat. No. 4,580,810. Both frontal and side impact crashes frequently have severe cross-axis accelerations.
Additionally, all-mechanical self contained airbag systems, such as disclosed in the Thuen patent, require that the sensor be placed inside of the inflator which increases the strength requirements of the inflator walls and thus increases the size and weight of the system. One solution to this problem appears in Breed, U.S. Pat. No. 4,711,466, but has not been implemented. This patent discloses a method of initiating an inflator through the use of a percussion primer in combination with a stab primer and the placement of the sensor outside of the inflator. One disadvantage of this system is that a hole must still be placed in the inflator wall to accommodate the percussion primer that has its own housing. This hole weakens the wall of the inflator and also provides a potential path for gas to escape.
Another disadvantage in the Thuen system that makes it unusable for side impacts, is that the arming system is sealed from the environment by an O-ring. This sealing method may perform satisfactorily when the module is mounted in the protected passenger compartment but it would not be satisfactory for side impact cases where the module would be mounted in the vehicle door where it can be subjected to water, salt, dirt, and other harsh environments.
Self-contained electrical systems have also not been widely used. When airbags are used for both the driver and the passenger, self-contained airbag systems require a separate sensor and diagnostic for each module. In contrast to mechanical systems the electronic sensor and diagnostic systems used by most vehicle manufacturers are expensive. This duplication and associated cost required for electrical systems eliminates most of the advantages of the self contained system.
Sensors located in the passenger compartment of a vehicle can catch most airbag-required crashes for frontal impacts, particularly if the occupants are wearing seatbelts. However, researchers now believe that there are a significant number of crashes which cannot be sensed in time in the passenger compartment and that this will require the addition of another sensor mounted in the crush zone (see, for example, Breed, D. S., Sanders, W. T. and Castelli, V. xe2x80x9cA Critique of Single Point Sensingxe2x80x9d, Society of Automotive Engineers Paper No. 920124). If true, this will eventually eliminate the use of self-contained airbag systems for frontal impacts.
Some of these problems do not apply to side impacts mainly because side impact sensors must trigger in a very few milliseconds when there is no significant signal at any point in the vehicle except where the car is crushing or location rigidly attached to this crush zone. Each airbag system must be mounted in the crush zone and generally will have its own sensor. Self contained airbag systems have heretofore not been used for occupant protection for side impacts which is largely due to the misconception that side impact sensing requires the use of elongated switches as is discussed in detail in U.S. Pat. No. 5,231,253, incorporated by reference herein. These elongated prior art side impact crush-sensing switches are not readily adaptable to the more compact self-contained designs. The realization that a moving mass sensor was the proper method for sensing side impacts has now led to the development of the side impact self contained airbag system of this invention. The theory of sensing side impacts is included in the ""253 patent referenced above.
In electromechanical and electronic self-contained modules, the backup power supply and diagnostic system are frequently mounted apart from the airbag system. If a wire is severed during a crash but before the airbag deploys, the system may lose its power and fail to deploy. This is more likely to happen in a side impact where the wires must travel inside of the door. For this reason, mechanical self-contained systems have a significant reliability advantage over conventional electrical systems.
Finally, the space available for the mounting of airbag systems in the doors of vehicles is frequently severely limited making it desirable that the airbag module be as small as possible. Conventional gas generators use sodium azide as the gas generating propellant. This requires that the gas be cooled and extensively filtered to remove the sodium oxide, a toxic product of combustion. This is because the gas in exhausted into the passenger compartment where it can burn an occupant and is inhaled. If the gas is not permitted to enter the passenger compartment, the temperature of the gas can be higher and the products of combustion can contain toxic chemicals, such as carbon dioxide.
These and other problems associated with self contained airbag systems are solved by the invention disclosed herein.
This invention is primarily concerned with a novel self-contained airbag system for protecting occupants in side impacts. This is accomplished by using the sensors described in U.S. Pat. No. 5,231,253 referenced above, along with other improvements described in detail below. This invention is secondarily concerned with applying some of the features of the novel side impact system to solving some of the problems of prior art all mechanical airbag systems discussed above.
The sensitivity to cross axis accelerations of current all mechanical airbag systems, for example, is solved in the present invention, as discussed in U.S. Pat. No. 5,233,141, incorporated by reference herein, through the substitution of a hinged sensing element for the ball sensing mass in the Thuen patent.
The problems resulting from the hole in the inflator wall when a percussion primer is used as in Breed, U.S. Pat. No. 4,711,466, are solved in the present invention through the placement of sensitive pyrotechnic material in a cavity adjacent to the outside wall of the inflator and then using shock from a stab primer to initiate the pyrotechnic material and thus the inflator. An alternate solution, as discussed below, is to make the size of the hole created in the inflator by the action of the stab primer small so that the total quantity of gas which escapes into the sensor is small compared with the quantity of gas used to inflate the airbag.
Finally, in the self-contained airbag system disclosed herein, provision is made to exhaust the gas outside of the passenger compartment, into the vehicle doors, or other side areas of the vehicle. This permits the use of higher gas temperatures and alternate propellant formulations, such as nitro-cellulose, which produce toxic combustion products. Both of these changes reduce the size, weight and cost of the system.
Briefly, the self-contained airbag system of this invention consists of a sensor having a movable sensing mass, means to sense the position of the sensing mass to determine if the airbag should be deployed, a sealed housing, a gas generator for producing the gas to inflate the airbag, an airbag, and mounting hardware.
The principal objects and advantages of this invention are:
1. To provide a self contained side impact occupant protection airbag system incorporating the advantages of a movable mass sensor resulting in a low cost, compact airbag system.
2. To provide a frontal impact all mechanical airbag system incorporating a hinged sensing mass to eliminate the effects of cross-axis accelerations on the operation of the sensor.
3. To provide a method of minimizing the leakage of the inflator gases out of the inflator portion of a self contained airbag system into the sensor portion and the associated problems.
4. To provide a side impact airbag system which utilizes the crush of the vehicle side to arm the sensor and motion of a sensing mass to initiate deployment.
5. To provide a method of hermetically sealing a self contained airbag system while permitting an external force to be used to arm the system.
6. To provide a more compact self contained side impact airbag system by providing for the exhausting of the airbag gas into the vehicle door or side, therefore permitting the use of higher temperature gas and propellants which would otherwise not be viable due to their toxic products.
7. To provide an all-mechanical airbag system utilizing a cantilevered firing pin spring which also provides the biasing force on the sensing mass thereby providing a simplified design.
8. To provide an all-mechanical airbag system with a thin sensor mounted outside of the inflator housing but in line with it to reduce the size of the system and permit the use of conventional inflator designs.
9. To provide a highly reliable side impact occupant protection electromechanical self-contained airbag system.
10. To provide a highly reliable side impact occupant protection electronic self contained airbag system.
11. To provide a method of obtaining the power for an electrical self contained airbag system from other components within the door thereby minimizing the requirement for separate wiring for the airbag system.
12. To provide a power supply within the self contained module and a simplified diagnostic system for an electrical self contained airbag system.
13. To provide a self contained airbag system design that permits the arming of the sensor after it has been mounted onto the vehicle but before the inflator is mounted to provide greater safety against unwanted deployments.
Other objects and advantages will become apparent from the discussion below.
In one embodiment of a side impact airbag system for a vehicle, the airbag system comprises a system housing defining an interior space and arranged on the first side of the vehicle alongside at least a portion of a passenger compartment of the vehicle, one or more inflatable airbags arranged in the interior space of the system housing such that when inflating, the airbag(s) is/are expelled from the system housing into the passenger compartment, and inflator means arranged at least partially within the interior space of the system housing for inflating the airbag(s). The inflator means comprise an inflator housing containing propellant. The airbag system also includes a crash sensor for initiating inflation of the airbag(s) via the inflator means upon a determination of a crash requiring inflation thereof The crash sensor comprises a sensor housing arranged within the system housing, proximate thereto and/or mounted thereon, and a sensing mass arranged in the sensor housing to move relative to the sensor housing in response to accelerations of the sensor housing resulting from the crash into the first side of the vehicle. Upon movement of the sensing mass in excess of a threshold value, the crash sensor initiates the inflator means to inflate the airbag(s). The threshold value may be the maximum motion of the sensing mass required to determine that a crash requiring deployment of the airbag(s) is taking place.
The crash sensor may be an electronic sensor and the movement of the sensing mass is monitored. The electronic sensor generates a signal representative of the movement of the sensing mass that may be monitored and recorded over time. The electronic sensor may also include a microprocessor and an algorithm for determining whether the movement over time of the sensing mass as processed by the algorithm results in a calculated value that is in excess of the threshold value based on the signal.
In some embodiments, the crash sensor also includes an accelerometer, the sensing mass constituting part of the accelerometer. For example, the sensing mass may be a micro-machined acceleration sensing mass in which case, the electronic sensor includes a micro-processor for determining whether the movement of the sensing mass over time results in an algorithmic determined value which is in excess of the threshold value based on the signal. In the alternative, the accelerometer includes a piezo-electric element for generating a signal representative of the movement of the sensing mass, in which case, the electronic sensor includes a micro-processor for determining whether the movement of the sensing mass over time results in an algorithmic determined value which is in excess of the threshold value based on the signal.
The inflator means may be any component or combination of components which is designed to inflate an airbag, preferably by directing gas into an interior of the airbag. One embodiment of the inflator means may comprise a primer. In this case, the crash sensor includes an electronic circuit including the accelerometer and the primer such that upon movement over time of the sensing mass results in a calculated value in excess of the threshold value, the electronic circuit is completed thereby causing ignition of the primer.
The system housing may comprise a mounting plate having a bottom wall and flanged side walls, the bottom wall having an aperture, whereby the inflator housing is arranged in the aperture. The system housing may be arranged inside a door of the vehicle or between inner and outer panels not associated with a door of the vehicle.
The airbag system may also include a capacitor arranged within the system housing to supply power to initiate deployment of the airbag system and an electronic diagnostic system arranged within the system housing to permit diagnoses of a fault within the airbag system.
Another embodiment of an airbag safety restraint system for a vehicle including an electronic crash sensor comprises an inflatable airbag having an interior, and an inflator assembly having an inflator housing, an ignitable gas generating material contained in the inflator housing and at least one passage extending between the gas generating material and the interior of the airbag such that upon ignition of the gas generating material, gas is generated and flows through the at least one passage into the interior of the airbag to inflate the airbag. The electronic crash sensor causes ignition of the gas generating material upon a determination of a crash requiring inflation of the airbag and comprises a sensor housing, a sensing mass arranged in the sensor housing to move relative to the sensor housing in response to accelerations of the sensor housing resulting from the crash whereby a signal representative of the movement of the sensing mass is generated, and a micro-processor comprising an algorithm for determining whether the movement of the sensing mass over time results in a calculated value which is in excess of a threshold value based on the signal. If the movement over time of the sensing mass results in a calculated value that is in excess of the threshold value, the micro-processor causes ignition of gas generating material and thus inflation of the airbag.
The sensor housing may be mounted proximate to the inflator housing. The crash sensor may include an accelerometer whereby the sensing mass constitutes part thereof, e.g., a micro-machined element, or the accelerometer may include a piezo-electric element. The inflator assembly may include a primer for igniting the gas generating material whereby the crash sensor includes an electronic circuit including the accelerometer and the primer such that upon movement of the sensing mass over time resulting in a calculated value in excess of the threshold value, the electronic circuit is completed thereby causing ignition of the primer.
Yet another embodiment of an airbag safety restraint system for a vehicle including an electronic crash sensor comprises, in addition to the inflatable airbag and inflator assembly described immediately above, a sensor housing, and an accelerometer arranged in the sensor housing and including a sensing mass movable relative to the sensor housing in response to accelerations of the sensor housing resulting from the crash. The accelerometer is arranged to generate a signal representative of the movement of the sensing mass over time. The crash sensor is arranged to cause ignition of the gas generating material if the movement over time of the sensing mass represented by the signal results in a calculated value that is in excess of a threshold value. The sensor housing may mounted proximate to or directly on the inflator housing. The sensing mass may be a micro-machined element. The accelerometer may also include a piezo-electric element for generating the signal. In another basic embodiment of the side impact airbag system in accordance with the invention, the system includes a system housing defining an interior space and which is arranged on the side of the vehicle alongside at least a portion of a passenger compartment of the vehicle, a sensor housing, a sensing mass arranged in the sensor housing to move relative to the sensor housing in response to accelerations of the sensor housing in excess of a predetermined threshold value resulting from impact into the first side of the vehicle, one or more inflatable airbags arranged in the interior space of the system housing such that when inflating, the airbag(s) is/are expelled from the system housing into the passenger compartment, and inflator means arranged at least partially within the interior space for inflating the airbag(s). The inflator means comprise an inflator housing containing propellant and the sensor housing is coupled to the inflator housing. The system also includes initiation means arranged in the sensor housing responsive to the movement of the sensing mass upon acceleration of the sensor housing for initiating the inflator means to inflate the airbag(s) and expel the same from the system housing into the passenger compartment.
The system housing may comprise a mounting plate having a bottom wall and flanged side walls, the bottom wall having an aperture in which the inflator housing is arranged. The inflator housing may include a first flanged housing section and a second housing section, the first housing section being arranged in the aperture such that a flanged portion of the first housing section abuts against the bottom wall, the sensor housing is connected to the first housing section. The sensor housing may comprise a top cover adapted to be situated most proximate an exterior of the vehicle and opposed wall portions cooperating to define a sealed interior space whereby the sensing mass is arranged in the interior space of the sensor housing. The initiation means may comprise a biasing spring arranged in the interior space of the sensor housing and releasably restrained by the sensing mass and a firing pin arranged in connection with the biasing spring.
In some embodiments, the sensor housing further comprises a bottom cover having an orifice arranged such that when the biasing spring is released from the sensing mass upon acceleration of the sensor housing, the firing pin passes through the orifice. In this case, the inflator means further comprise a stab primer located in the inflator housing adjacent the orifice and in a position to be impacted by the firing pin.
In the alternative, the stab primer is arranged in the interior space of the sensor housing in a position to be impacted by the firing pin when the biasing spring is released from the sensing mass upon acceleration of the sensor housing whereby initiation of the stab primer creates a shock which is transmitted through the sensor housing to the inflator assembly. The inflator assembly includes a shock sensitive pyrotechnic mix that ignites upon impact by the shock created upon initiation of the stab primer. The sensor housing thus may comprises a solid bottom cover arranged alongside the inflator housing.
The sensing mass may be pivotally coupled to the sensor housing to enable the mass to pivot about a vertical axis in response to accelerations of the sensor housing in excess of the predetermined threshold value resulting from impact into the side of the vehicle. The sensing mass may be substantially planar and square. The sensing mass may be arranged in the sensor housing for movement relative to the sensor housing only in response to accelerations of the sensor housing caused by the impact into the side of the vehicle.
Sealing means may be provided for hermetically sealing the sensor housing to prevent passage of moisture and contaminants into or out of the sensor housing. In one embodiment, the sealing means comprise a member cooperating at least with the inflator housing to surround the sensor housing within a closed, hermetically sealed compartment. When the inflator housing has first and second housing sections, the member may comprise a tubular section surrounding the first housing section of the inflator housing and a spherical section sealing an end of the tubular section and being situated over the sensor housing.
The sensor housing may comprise a side wall, a hinge for pivotally attaching the sensing mass to the side wall, and a releasable firing pin restrained by the mass. The inflator means are initiated by movement of the firing pin. The system housing is mounted such that upon a side impact causing acceleration of the sensor housing in excess of the predetermined threshold value, the sensing mass pivots about the hinge causing release of the firing pin, and thus initiating the inflator means to inflate the airbag(s). This sensing mass may also be cantilevered where the attachment to the wall performs the function of a hinge as in certain micro-machined accelerometer designs.
In some embodiments, crush detecting means are provided for preventing movement of the sensing mass in response to accelerations of the sensor housing in excess of the predetermined threshold value resulting from impact into the first side of the vehicle until crush of the first side of the vehicle is detected. Thus, the sensor will actuate only upon crush of the vehicle and a sufficient velocity change. The crush detecting means comprise a sensor can surrounding the sensor housing and including an outer cover and a tubular wall defining an interior space in which the sensor housing is situated. The crush detecting means may also include a spherical pusher member adapted to receive a force from the outer cover upon crush of the first side of the vehicle, a first lever adapted to be pushed by the pusher member and hingedly mounted at one end thereof to the sensor housing to enable it to rotate about an attachment point to the sensor housing, and a second lever hingedly connected at a first end to the first lever and pivotally connected to the sensor housing. The second lever has a second end extending through an aperture in a wall of the sensor housing and restraining the sensing mass from movement whereby rotation of the second lever causes the second end of the second lever to pull out of the sensor housing.
The vehicle may include a pusher plate arranged in a side door on the first side of the vehicle whereby the system housing is arranged alongside at least a portion of the pusher plate.
In certain embodiments, the initiation means comprise a first electrical spring contact biased against the sensing mass and a second electrical contact arranged on the top cover of the sensor housing whereby upon movement of the sensing mass, the first contact is caused to engage the second contact and complete an electrical circuit.
As to mounting of the system housing, the system housing is mounted such that the sensor housing is usually closer to an exterior of the side of the vehicle than the inflator housing and thus more forwardly in a side impact crash direction than the inflator housing. The system housing may be arranged inside a door of the vehicle or between inner and outer panels of a section other than the door of the vehicle.